Our GM SM420 adapter to the Dana 18 / 20 is 4.00” in length. The adapter material is 356 T-6 heat treated aluminum alloy, and the adapter has a provision for a transmission mount. Our kit will include a adapter housing, spud shaft with 10 spline for drive gear, mount block, gaskets, seal, nylon lock nut, and adapter instructions.
This adapter assembly will fit the Dana Spicer 18 / 20 with a 10 tooth female drive gear. The transfer case index to the new adapter will require an index retainer & sealed bearing. Please I.D. the transfer case bore size (3-1/8”) small hole or (4”) large hole for proper retainer. Additional information can be obtained in our on-line catalog, Jeep & Scout Vehicle Section: Transfer Case Information, Jeeps 1941-79.
The kit is designed for exclusive use with the GM SM420 4 speed transmission. The SM420 was used in GM trucks 1947 to 1968 and has a 10 spline output shaft and was used in both 2wd and “divorced” 4wd applications.